The goal of this research is to elucidate on the basis of a mixed longitudinal design the changes in cardiac structure and function which occur during late childhood and adolescence. Four aims are presented: 1) to document the nature and extent of changes in cardiac structure, based on M-mode measurements and indices and develop corresponding reference values; 2) to document the nature and extent of GENDER AND MINORITIES Of the 678 participants enrolled in Project HeartBeat!, 136 (20.1%) were African-American, 506 (74.6%) were Caucasian, 25 (3.7%) were Hispanic, 7 (1%) were Asian, and 4 (0.6%) were Native American. 333 (49.1%) were female and 345 (50.9%) were male. Completeness of follow-up by gender and ethnicity is not provided. 81.4% of the total study group attended all scheduled examinations, and 90.9% of subjects eligible for at least 10 examinations completed 10 or more exams. BUDGET Under Other Expenses in Year 1, the budget for "Publications, presentations, (graphics, page charges)" is reduced from $1000 to $250, since most of the costs incurred in this category will occur in Year 2. Two full years at the FTE proposed appears excessive for the work described, given the expertise of the team. It is recommended to reduce the funding period to 18 months, and therefore reduce the requested budget for Year 2 by one-half.